The purification treatment of waste gas or water discharged from factories and other facilities has been an important problem for a long time, and recently it became a more urgent problem, as the polution problem became a subject of much discussion. Many processes of treating waste gas or water have been proposed, but among these a process of using active carbon is widely adopted.
Active carbon is a favorable reagent because of its strong adsorptive power, but it must be regenerated in case of reuse, when it becomes inactive as the adsorption goes on and it becomes saturated with adsorbed matter. In the conventional method for activating and regenerating used active carbon, the same is heated, as for instance, in an oil fired rotary kiln at a temperataure of 800.degree. C. or higher, and water vapor is introduced concurrently to regenerate the carbon by a process of water gas reaction.
However, this method requires prolonged heating at such high temperature, so that it needs a considerable amount of fuel, as well as an expensive installation cost. Further, there is an excessive burning loss of the active carbon.
It is also known to use Joule's heat generated by conducting electric current through the active carbon for heating the same and desorbing or liberating adsorbed material, but this method also needs expensive installation cost, especially for the electrical equipment, as it requires very heavy current.
After repeating many experiments to find out an efficient and economical method for regenerating used active carbon, one of the inventors of the present invention developed and disclosed an apparatus, in which vibration is applied to the active carbon powder while conducting electric current so as to generate spark discharges between particles of the active carbon and liberate the adsorbed material.
(For reference:
Publication of Japanese Patent Application Disclosure No.52-6393 and PA1 Japanese Utility Model Registration Application Disclosure No.52-14351)
However, it was found that this process still has the following disadvantages: With carbon particles which contact a longer time with each other, Joule's heat generates locally and consumes a large amount of current, and this causes lowering of efficiency. This also causes difficulties in controlling temperature during the operation, and becomes difficult to recover liberated or desorbed material, even if it is useful, as it decomposes at such high temperature caused by Joule's heat.